Method of manufacturing piston rings



April 23,1929. A MUMMERT l I 1,710,064

METHOD 0F MANUFACTURING PISTON RINGS 'Filed July 14, 1927 Patented pr. 23, 1929.

UNITED .STATESy ri-x'rENTg OFFICE.

ARDEN JOI-IN M'UMMERT, OF ''NVERSTTY CITY, MISSOURI, ASSIGNOR TO IVICQTKJ'AY-y MORRIS MANUFACTURING COMPANY, OF ST. LOUIS, MISSOURI, A CORPORATION OF DELAWARE.

METHOD ylillANUFA@TUIR/ING PISTON RINGS.

Application led July 14, 1927. Serial No. 205,671.

My invention relates to methods of manufacturing piston rings and more particularly to methods of manufacturing resilient rings such as are used on reciprocating pistons of internal combustion engines, air compress sors, steam engines, and other like devices an d which are manufactured from cast n rings which are of a predetermined out-of-round shape.

rlhis cast ring is as stated of an out-ofround shape larger in circumference than is the finished ring to be produced so that a scction, representing the diiference in circumference of the cast ring and the finished ring may be cut from the cast ring when it is split. Then when the ring with the section cut therefrom is closed,that is, when the two ends of the split ring are brought together, the ring thusl formed will be a perfect circle and the radial stress throughout the closed ring will be approximately uniform at all points on the circumference of the ring and there will be a resultant approximate uniform radial pressure of the ring upon the cylinder wall. If a concentric ring was cast and then split and no section of the ring was removed the radial pressure of the finished ring at points nearest the split would be substantially great er than at points away from the split along the circumference of the ring. Also, if the ring was cast in a circular shapeand then a section was removed the linished ring would not be a perfect circle when closed. f

Since the cast rings are not `round it is diliicult to machine them in that shape, and therefore, in most cases he ring castin are split before the ring is machined and. this practice often results in' great waste since sometimes during the machining a defect will be encountered in the ring and the ring will have to be discarded and returned to the 'foundry to be melted and recast. llVhen this happens the labor of splitting the rin is lost and this labor is costly especially when the rings are split so that theadjacent ends form a scarf or lap oint.

Several vattempts have been made to machine they casting before it is split so that :if defects are :encountered during the machining the ring may be scrapped without losing the cost of the splitting operation. Such atn wedging is exerted against one corner of the The outer and inner faces of ring only. the ring at their sides nearest this corner are forced slightly outwardly into aposition at a greater radial distance, from the axis of the ring than the portions of the outer and inner faces nearest the edge of the ring at which no pressureis exerted. Vhen the cast'- ing :is machined while held in circular shape in this manner a different amount of Ametal is taken oif of the outer face aty different points in its width. At points close to the edge of the ring upon which the pressure is exerted by the cone a comparatively great amount of metal is taken oli' and at points farther away from the edge of the ring against kwhich the wedging is effected less metal is taken oli'. kAs a result when the ring has been machined it is in cross-section somelwhat wedge sh ape and is thinner at one side than at the other. Consequently the ring loses much of its'eiiiciency and effectiveness to maintain con'iprcssionY when placed in use vto a uniform thickness thereby assuring uni- ,forni radial pressure of the inished ring when used in an engine; and to provide a method of manufacturing a piston ring in which the o uter face of the ring is machined he'l'orethe ring is split.

My new and improved method of manufacturing pistonA rings in its broadest sense includeskcastiug the ring in a predeteriuined out-ofround shape, then forcing the ring into circular kshape by pressure exerted radially outward from within the ring7 and n cast ringis then placed on the collet A oi the,

then machining` the ring while it is in circular form.

One of the many forms oi" devices which maybe used toeXert pressure radially outwarddron'i within the ring to change the shape ot the ring` without distorting` it.l is shown somewhat diagranimatically in the aC- company/'ing` drawings .wherein similar letters are used to designate similar parts. Fig. l is a sectional view ot the head stock or" the r.lathe on which the ring; is to ybe machined; Figs. 2 and 3 iront Y. iews oi the head stock showing, respectively, the ringand collet betore pressure is exertedgon the ring by eX- pandingA the collet and .the ring and collet after Vthe collet has been expanded to exert radial pressurey against the inner tace ot the ring.

Referring to the figures the collet A which has its outer end toi-ined Vby a .plurality of segments B is carried by the .head stool: C ot the lathe. The lower tac-es et the outer ends of the segments B are berclcd as at Dat an angle to conform with the angle ot the flare E arranged on the outer end ot the collet pull harF. Preferably, shoulders u@fare arranged on the outer sides ci the sepinen ts B `for the purpose more fully ,hereinatter dis-v closed. Anysuitable meansi not shown, may be provided to. move the pull bar llfinwardly to evpandV the segments B or to move it outwardly to allow thc seginents to collapse.

' The practice ot my new and improved method ot manufacturing piston Vrings usingthe device shown in the rdrawings and de'- scribed above is yas follows: The ringis lirst cast in a predeterminerL out-otround shape. This cast rin` H is then, preferably, rough ground on its inner iace to remove any burrs or other short projections whichv are'due'to slight imperfections in the sand mold. he

head stock ot the lathe with thev segments B in collapsed position. lt the segments ot the collet are provided with the shoulders G one edgeorr the ring is place-d against these shoul-V ders and-the ring H will be registered in a plane at substantially right angles to the axis 'ot Athe collet." The pull barld1 is then moved inwardly so that the Hare E thereon actinagainst the beveled lower edges l) 4ot the segments B willenpand the segments and thercby exert pressure radially from withinV the ring` against the innertace thereof to torce the ring` into circular shape.

TVith the ringv maintained in Vthis position the head stock of the lathe is turned and the outer tace of 'the ring is machined. 'i Since the ring is forcedinto circular shape by apressure exerted radilly from within the ring during` the machining` of the outer face a uniiorm amount ci metal will be removed and the Yfinished ring will loe of uniform thiol;-

ness. y

Vvlitter the machiningis'compl'eted the'pull utacture without'deviating rfrom the spirit of my invention as embodied in the claims inclinlcd below. 'However7 in any practice of my improvedmethod I prefer that thepressure to `torce the ring into circular shape be eXertedin a manner so that they ring will not bi'idistortcd to carry one side of the ring `:tur-

ther outwardly than -the other side of the ring.

lllhat vlclaim as new and desire to secure by Letters Patent, is

l.' A method 'ot manufacturing a piston ring which includes casting a continuous ring Y in a predetermined out-of-round shapegorcingsaid continuousringl into' circular shape by pressure exerted against the :Zone of the inner tace ont said ring, and then machining said ring` while it is maintained in circular shape.

2. A meth-.odl ot manufacturing a piston ring which includes casting a continuous ring in a predetermined outot-round shape, rough grinding the inner tace ot said ring and then forcing` ,said continuous ring into circular shape byy pressure exerted radially outward troni withinsaid ring againstsaid zone 'of thc inner tace, and then machining said ring while it is maintained in circular shape.

3. i ine'hod ot manuiacturing a piston ring` which includes castinga continuous ring in a predetermined out`ot-round shape, rough grinding the inner Yface of said ring, then forcing said continuous ring into circular shape by pressure exerted radially outward against said Zone of the inner tace7 machiin in g said ringl Awhile it is maintained in said circular shape, and then splitting and finishing said ring.

llO

a. A method of manutacturing a piston v.

ring` which includes casting a continuous ring in a predetermined outfo-fround shape, forcing` said continuous ring into'circular shape by ypressure exertedV radially outward from within said ring against the Zone 'of the inner 1 `tace thereof and-then machiningthe outer tace of said ring` while it is maintained in circular shape. c i

5. A method of manufacturing al Apiston. which includes casting a continuous rin g in a predetermined outset-round shape, rough grinding the inner faceof said rin g, and then Vforcing` said continuous ring into circular shape hy pressure exerted radially outward from within said ring against the zone ot the inner` tace thereof and then machining saidV ring` while it is maintained in circular shape.

6. A method of' manufacturing a piston ring which includes casting a continuous ring in a predetermined outeoround shape, foreing said Continuous ring into circular shape 5 by pressure exerted radially outward from within Said ring against the Zone of the inner face thereof, machining Said ring While it is maintained in circular shape, removing said pressure and allowing said ring to resume Said out-o-round shape, and then splitting 10 and finishing said ring.

In Witness whereof I have signed my name to the foregoing specification.

ARDEN JOHN MUMMERT. 

